The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to form pulse width modulated (PWM) power supply controllers. One important characteristic of the PWM controllers was the efficiency. Many PWM power supply controllers changed operating modes based on the amount of current required by the load. In some controllers, a continuous conduction mode was used when the current required by the load was large and a burst mode was used when the current required by the load was low. However, the burst mode often resulted in a large ripple voltage in the output voltage. While operating in the burst mode, the operating frequency often resulted in the PWM controller producing audible noise. Additionally, the PWM controllers needed complicated logic to switch the PWM controller between the two operating modes.
Accordingly, it is desirable to have a PWM controller that has high efficiency during light load conditions, that reduces the ripple voltage in light load conditions, that can reduce the audible noise, and that reduces the amount of control logic.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.